Device for producing an oscillatory circuit tuned to an ultrahigh frequency



April 1, 1952 J. O- STRUTT ET AL DEVICE FOR PRODUCING AN OSCILLATORY CIRCUIT TUNED TO AN ULTRAHIGH FREQUENCY Filed July 13, 1946' NVENTORS.

I IHAXIMILIAAIVc/ULIUJ UTTUSTRl/Z'T ALBERT PAIFDEJZZZEL A T TFRNE Y.

Patented Apr. 1, 1952 2,591,316 ICE DEVICE FOR PRODUCING AN OSCILLATORY CIRCUIT TUNED TO AN ULTRAHIGH FRE- QUENCY Maximiliaan Julius ()tto Strutt, Aidert van der Ziel, and Kornelis Swier Knol, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn, as

trustee Application July 13, 1946, Serial No. 683,306 In the Netherlands March 6, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 6, 1963 Claims.

For producing ultrahigh frequency oscillations it is already known to utilize a sc-called diode generator constituted by a diode, the cathode and the anode being connected with the alive extremities, or forming part of the alive extremities of an oscillatory circuit tuned to the frequency to be produced and the voltage which is supplied to the anode and which is positive relatively to the cathode inconnection with the distance between the cathode and the anode being given such a value that the transit time of the electrons is approximately a whole period or a whole number of periods of the natural frequency of the oscillatory circuit increased by a quarter of period.

In this known device the effective mutual conductance and hence the efiiciency is generally very small. An important reason for this is that the transit time of the electrons from the cathode to the anode is comparatively great, so that several of the concentrations and dilutions of the electrons produced under the action of an alternating voltage set up at the anode simultaneously occur in the space located between the electrodes connected to the ends of the circuit. These concentrations and dilutions jointly influence a but small alternating charge on the anode, since the concentrations and dilutions occurring simultaneously counteract each other.

The present invention is based on the recognition of the fact that the effective mutual conductance and hence the efiiciency of a device of the above-mentioned kind in which the transit time of the electrons is utilized to reduce the damping of an oscillatory circuit, that is to produce a negative resistance between the alive extremities of the circuit, may be improved by arranging between the cathode and the anode an electrode which allows the passage of electrons and which is connected to the cathode for oscillations having the naturalfrequency of the oscillatory circuit, the damping of which is to be reduced.

In the device according to the invention, the alternating charge influenced on the anode is determined by the transit time of the electrons between the grid and the anode, which transmit time may be small due to the positive potential of the anode. Preferably, care is taken to see to it that the time in which the electrons cover the distance between the grid and the anode is not greater than a half cycle, so that only one concentration or dilution of the electronic current invariably exists in the space located between the grid and the anode.

In order that the invention may be more clearly understood and readily carried into effect, it will be described more fully by reference to the accompanying drawing.

In the drawing:

Fig. 1 is a schematic circuit of an oscillator in accordance with the invention.

Fig. 2 is a cross-sectional showing of a preferred embodiment of a high-frequency oscillator structure in accordance with the invention.

Fig. 3 is a cross-sectional showing of a highirequency mixer structure in accordance with the invention.

Fig. 4 is a cross-sectional showing of a highfrequency amplifier structure in accordance with the invention.

Fig. 1 shows a device for producing oscillations which comprises a discharge tube containing a cathode 2, a grid 3, and an anode 4. An oscillatory circuit 5 tuned to the frequency of the oscillations to be produced in circuit 5 is included between cathode 2 and anode 4. According to the invention, grid 3 is connected to the cathode for the oscillations to be produced.

The described device permits of producing oscillations in circuit 5, if the phase displacement between the alternating voltage set up at the anode t and the current in the anode circuit amounts to approximately or an odd number of times of 180, since in this case a negative resistance exists between the electrodes connected to the alive extremities of circuit 5. Due to the grid which exists between the cathode and the anode, the electrons dislodged at the cathode under the action of an alternating voltage set up at the anode will not influence an alternating charge on the anode before the electrons have passed grid 3. Consequently, With a transit time between the grid and the anode, which is negligible relatively to the transit time between the cathode and the grid, a phase displacement between the alternating voltage set up at the anode and the alternating charge thus produced in the anode circuit will substantially be determined by the time in which the electrons cover the distance between the cathode and the grid. Consequently, the phase displacement required for the production of oscillations may be obtained, for example, by giving the transit time of the electrons between the cathode and the grid a value of the order of magnitude of a half period of the oscillations to be produced, whereas the transit time of the electrons between the grid and the anode is small relatively thereto.

The voltage supplied to the anode 4 is preferably given such a value that the phase displacement between the alternating voltage set up at the anode and the current flowing in the anode side the cavity resonator 9 is a hairp'enda of the natural frequency of the cavity resonator, or less.

. The cavity resonator 9 is traversed by the eleccircuit is approximately 180, which is achieved with a transit time of the electrons between the cathode and the grid, which is of the order of magnitude of a half period of the oscillations to be produced, and a transit time of the electrons between the grid and the anode, whichis less than a half period. In a device in which dilutions is avoided, resulting in ahigher effective mutual conductance.

Fig. 2 shows a form of construction of the device shown in Fig. l which is preferably used for the production of ultrahigh-frequency oscillations. In this form of construction cathode 2 and anode 4 form part of the alive extremities of an oscillatory circuit 5, the damping of which is to be reduced and which is constituted by a so-called cavity resonator. The term cavity resonator is to be understood to mean a vessel of conductive material which is closed substantially on all sides and which surrounds a hollow space of arbitrary shape. Cathode 2 is arranged in an aperture of one of the two parts of the wall of the cavity resonator which are in parallel opposite to each other and coupled capacitatively with this part of the wall. Anode 4 is constituted by that part of the wall which is opposite to the cathode. Like in the device shown in Fig. l, cathode 2 and anode 4 have arranged between them a grid 3 which is connected to cathode 2 for oscillations having the natural frequency of the cavity resonator 5. The latter has supplied to it:a voltage positive relatively to the cathode. This voltage, in connection with the length of the path of the electrons inside the cavity resonator, is given such a value that the transit time of the electrons from the cathode to the grid is approximately a half period of the oscillations to be produced and from the grid to the anode less thana half period of the oscillations to be produced. With this proportioning the device produces oscillations the frequency of which cor- 'tronic current after it has passed the cavity resonator 5, due to which the electronic current concerned is modulated in density by oscillations produced in the cavity resonator 5. These concentrations and dilutions of the electronic current influence a charge between the front and the back of the cavity resonator 9, due to which oscillations having the natural frequency of the cavity resonator 5 may be derived from the cavity resonator 9 by means of a coupling 100p Hi.

In the form of construction shown in Fig. 2, the cavity resonator 5 constitutes a vacuous vessel in which theelectronic current is produced,

" whereasin the devices shown in Figs. 3 and 4 the responds to the natural frequency of the cavity a resonator. The oscillations produced may be derived from the cavity resonator 5 by means of a coupling loop 6.

In the form of construction shown in Fig. 3 the anode 4, which constitutes a part of the wall of the cavity resonator 5, is perforated while a collecting electrode 1 is located on that side of anode 4 which is remote from the cathode. Electrode 1 has suppliedto it a voltage negative relatively to anode 4, due to which the electrons are greatly decelerated before impinging on electrode 1. This results in a but small loss of energy and an increase in efiiciency of the device. In this form of construction the whole device is housed in a vacuous vessel 8.

- Fig. 4 shows a form of construction of a device according to the invention in which a second cavity resonator 9 having the same natural frequency is arranged between the perforated anode 4 and collecting electrode 1. The cavity resonator 9 has supplied to it a voltage which is positive relatively to the cavity resonator 5 and which, in view of the length of the path of the electrons in the cavity resonator 9, is given such a value that the transit time of the electrons inthe electronic current is producedjin suclrmannor that the cavity resonator(s) may be arranged outside this vessel. In this case the vacuous vessel will usually have a tubular shape and contain only the cathode 2, the collecting electrode 1 and the grid 3, the latter of which may be connected to the cathode inside the vessel or not. Furthermore, it may particularly be mentioned that it is not necessary for the grid 3 to be connected to the cathode through the intermediary of a conductor, as is indicated in the forms of construction shown. If desired, use may be made of a capacitative connection of low impedance for the oscillations to be produced, in which case the transit time of the electrons may be controlled not only by the anode voltage but also by a direct voltage supplied to the grid.

The device shown in Fig. 3 is particularly adapted to the frequency transformation of highfrequency oscillations. To this end, the oscillations to be transformed are supplied to the cavity resonator by means of the coupling loop 6 while the auxiliary oscillation is produced in the cavity resonator 5 in the described manner. A highfrequency oscillation having a frequency equal to the difference frequency of the two oscillations may be derived from an oscillatory circuit which is tuned to this frequency and which is included in the external circuit of the collecting electrode 1. If the difference in frequency of the two oscillations to be mixed is comparatively great, it is also possible for the oscillationsto be. transformed in frequency to be supplied between the grid 3 and the cathode 2, since in this case a.

condenser which is included between the grid 3 and the cathode 2 and which constitutes a shortcircuit for oscillations having the natural frejusted in such manner that oscillationdoes v not] occur, it is true, but the damping of circuit 5 is nevertheless greatly reduced. With such an adjustment the device shown in Fig. 4"is' particular 1y adapted to the amplification of oscillations. The oscillations to be amplified may be supplied to the cavity resonator 5 by means of the coupling loop 6 whereas the amplified oscillations may be derived from the cavity resonator 9 by means of the coupling loop 10.

What we claim is: I

1. A high frequency electronic device comprising a cylindrical cavity resonator having opposing end walls in parallel relation, one of said walls having a centrally disposed outwardly projecting tubular recess, the other of said walls having an aperture inaxial alignment with said recess, an electron discharge system provided with a tubular electron-emissive cathode coaxially disposed within said recess, a control grid interposed between said walls and directly connected to said cathode, an anode constituted by said other of said walls and a collector electrode exterior to said resonator and juxtaposed and in axial alignment with said aperture, and a source of potential connected between said cathode and said anode, said collector electrode being connected to an intermediate point in said source, the magnitude of said source and the distances between said electrodes having respectivevalues at which the transit time of the electrons between the grid and the anode is less than a half period of the natural frequency of said resonator and at which the transit time of the electrons between the cathode and the anode produces a negative resistance effect.

2. A device, as set forth in claim 1, further characterized by the fact that the transit time of the electrons between the cathode and grid is substantially equal to a half period of said frequency.

3. A device, as set forth in claim 1, further including coupling means to inject high frequency energy into said resonator having a frequency at variance with the resonance frequency of said resonator, and means coupled to said collector electrode to derive therefrom an output wave whose frequency corresponds to the'difierence between the resonance frequency and the energy frequency.

4. A high frequency electronic device comprising first and second cylindrical cavity resonators having like natural frequencies, said fresonators having opposing end walls in parallel, relation,

said resonators being colinearly juxtaposed, ad-

resonator having a centrally disposed tubular recess projecting outwardly therefrom, the other end wall of said second resonator having a central aperture, an electron discharge system provided with a tubular cathode coaxially disposed within said recess, a grid directly connected to said cathode and interposed between the end walls of said first resonator, a first anode constituted by the apertured wall of said first resonator, second and third anodes constituted by the apertured walls of said second resonator and a collector electrode juxtaposed to the aperture in said other end wall of said second resonator and externally of said resonator, and a source of potential connected between said cathode and said second and third anodes, said collector electrode and said first anode being connected to intermediate points in said source, the magnitude of said source and the distances between said electrodes having respective values at which the transit time of the electrons between the grid and the first anode is less than a half period of the natural frequency of said resonators and the transit time of the electrons between the cathode and grid is substantially equal to a half period of said frequency.

5. A device as set forth in claim 4 further ineluding means for injecting high frequency energy into said first resonator, and means for extracting high frequency energy from said second resonator.

MAXIMILIAAN JULIUS OTTO STRU'IT. ALDERT VAN DER ZIEL. KORNELIS SWIER KNOL.

REFERENCES CITED The following references are of record in the file of this patent:

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